Like carbon dioxide, methane is one of the most important greenhouse gases. After a period of stagnation around 2000, atmospheric methane concentrations started to rise again in 2007. So far, the causes have been unknown. According to the recent study of climate scientists of Karlsruhe Institute of Technology (KIT), at least 40% of this increase result from the growing production of oil and natural gas in the northern hemisphere. The results are now published in the “Atmospheric Chemistry and Physics” journal. (DOI:10.5194/acp-16-3227-2016)

“The attribution to thermogenic methane from the oil and natural gas industry is based on our vertical measurements of ethane and methane concentrations between the ground and the uppermost layers of the Earth’s atmosphere,” says the initiator of the study associate professor Ralf Sussmann of the Atmospheric Environmental Research Division of KIT’s Institute of Meteorology and Climate Research (IMK-IFU). Ethane is essential for quantifying the contribution of thermogenic methane. Like methane, it is a hydrocarbon compound and one of the main components of natural gas. In case of biogenic methane sources, no ethane is produced.

The study is based on long-term measurements by the KIT team at the NDACC site at the Zugspitze summit and by climate researchers of the National Institute of Water and Atmospheric Research at the NDACC site Lauder, New Zealand. The column measurements are representative of the background concentration of methane and ethane in both hemispheres of the Earth. While measurements at the Zugspitze show a significant correlation between ethane and methane, i.e. a sudden increase of the concentrations of both trace gases from 2007 onwards, the Lauder scientists have observed a similar renewed increase for methane only. From these measurement results, the scientists concluded that at least 40% of the worldwide methane concentration increase after 2007 have to be attributed to the oil and gas sector and that the emissions took place in the northern hemisphere.